An exhaust manifold of this type is known from EP 1 426 557 A1.
A technical problem occurring in the case of exhaust manifolds of this type is thermal expansion which occurs both between the exhaust pipe bends themselves, but also between said pipe bends and a supply gas duct of the turbine housing of an exhaust-gas turbocharger connected to the exhaust manifold. This thermal expansion has to be compensated for in order to avoid damage. If the exhaust manifold is designed as a double-walled, air-gap-insulated (AGI) manifold, use is made as compensators therefor of internal sliding fits which are not, however, gastight, since the pipe components forming the sliding fits are merely plugged one inside another, but are not welded in a gastight manner to one another. However, the leakages which occur as a result at the inner pipes of the AGI manifold smooth the exhaust pressure pulsations which are needed in the case of twin scroll applications for better utilization of power and therefore for increasing performance. Sliding fits at the connecting points result in the volume surrounding the pipe components and being formed by the outer, gastight casing being filled and emptied by the exhaust pressure pulsations.
The composition of the exhaust mixture in said outer volume changes, for example, with the degree of flushing of the cylinders with fresh air.